The present invention relates in general to an adjustable pneumatic supporting surface, and more particularly, to adjustable pneumatic supporting surfaces responsive to variable loads and different human tissue types.
Alternating pressure mattresses have been in existence for at least 75 years. Segmented air mattresses first came into existence around 1910. U.S. Pat. No. 945,234 describes a pneumatic mattress that in many respects is similar to the low air loss surfaces sold today. Other examples are disclosed in U.S. Pat. Nos. 802,526, and 1,296,359. In 1930, J. D. Hart invented the first pump-driven alternating pressure air mattress. With the exception of the more recent low air loss feature, it is in many respects identical to what is commercially known today. This art is described in U.S. Pat. No. 1,772,310. This patent addresses the problems of bedsores and the concept of shifting the pressure from different portions or areas of the skin with an automated apparatus driving air bladders. U.S. Pat. No. 2,415,150 discloses a pneumatic mattress with small individual cells. An alternating pressure mattress commonly known as a “ripple mattress” is disclosed in U.S. Pat. No. 2,719,986. This particular design of mattress was widely copied and improved upon. Examples of these improvements are disclosed in U.S. Pat. No. 4,197,837. The valve controller system for the mattress was further improved upon as disclosed in U.S. Pat. No. 4,825,486.
Air bladders became known to rotate the entire body as disclosed in U.S. Pat. Nos. 5,003,654, 5,142,719, 5,152,021, 5,603,133, and 5,802,645. Another example is disclosed in U.S. Pat. No. 5,103,519. Rather than rotating the patient in order to reduce bedsores, U.S. Pat. No. 5,267,364 discloses a mattress configured to provide therapeutic waves. In these patents and others to follow, the focus shifted toward reducing the labor required to properly care for a bed-ridden patient. In this case, the patient is being physically rotated by a machine rather than a person.
In another effort to reduce the labor of patient management, there is disclosed in European Application No. EP0168213A2, a servo controlled alternating pressure mattress. The advantage of this mattress is that the equipment operator is no longer involved in adjusting the mattress pressure controls, as this is done automatically through a pressure transducer, which is interfaced to a microprocessor. By measuring the static pressure in the pressure relief surface it is possible to automatically ensure that the air bladders are properly filled at all times. The type of servo utilized in this controller, and in currently employed technology, is a simple limit servo, also known as a bang-bang servo. These systems make their decision on the correct operation of the surface through amplitude measurements of the surface's internal pressure. This approach is disclosed in U.S. Pat. Nos. 5,487,196, 5,044,029, and 6,928,681. The concept of servo control was further expanded by the use of pre-set pressure profiles and a feedback control system. This concept is described in U.S. Pat. No. 4,797,962; see also U.S. Pat. Nos. 5,963,997, 7,287,289, and 5,983,429. Specialized feedback controlled mattresses such as those which treat heel pressure management are disclosed in U.S. Pat. Nos. 5,666,681 and 6,151,739.
The use of limit type servo mechanisms to provide uniform pressure in hospital mattresses and transportation seating is known. An example of a servo controlled transportation seat is disclosed in U.S. Pat. No. 5,930,152. Another example is disclosed in U.S. Pat. No. 4,542,547 which describes a photo-electric control system. A completely mechanical mattress, which provides floatation through servo control, is disclosed in U.S. Pat. No. 5,237,501. Yet other examples which use photo-control are disclosed in U.S. Pat. No. 6,560,804 and U.S. Patent Application No. 2006/0179579A1. Examples of mattresses which utilize electronic control in a pneumatic system are disclosed in European Application No. EPO489,310A1, and U.S. Pat. Nos. 5,687,099, 5,815,864, and 7,107,642. The mattresses use a static pressure measurement which may be a voltage that corresponds to patient pressure as disclosed in the '642 patent, the position of a potentiometer or LVDT as disclosed in the '501 patent, a resistive plastic pressure sensing sensor or a conventional pressure transducer which is utilized in the '310A1 and '099 patents, or a photo-electric limit switch as disclosed in the '547, '804 and '579A1 patents. The use of rate of change rather than a static measurement is disclosed in U.S. Pat. No. 5,915,864 to provide mattress pressure stability.
While these prior art alternating pressure low air loss mattresses reduce the amount of labor required to care for a patient, these mattresses fall short of modern day requirements. For example, they require the use of fixed menus in order to provide the best therapy protocol for the patient. Further, the prior art does not anticipate the legal environment in which hospitals operate today, where there is a need to regularly record and store surface pressure-map information to establish that the patient was receiving optimum surface therapy at all times. The current prior art not only does not anticipate these needs but furthermore, it is not capable of collecting this information because the wrong type of measurements are being used to provide the feedback information for the servo controlled mattress systems.
Since clinical assessment is currently done based on the appearance of the skin, identification of the tissue bearing the load will have significant implications for prevention of the development of pressure ulcers. This automatic characterization of tissue type is enabled by utilizing the present invention. Thus it is possible not only to characterize the weight of the tissue that is above a particular location on the air bladder array but also the type of tissue. With these two pieces of information the microprocessor in the mattress control system will be able to completely characterize the type of patient who is on the surface and where they are located on the surface, for example, the patient's buttocks (adipose tissue) and feet (bony tissue) which possess distinctive frequency spectra.
The escalation of medical costs as led to attempts in the past to streamline the treatment for the prevention of bedsores. Attempts to implement uniform treatment measurement scales, such as the Braden Scale, have heretofore been thwarted by inexact methods of gathering statistical information relevant to the patient's bedsore condition. Certain, rudimentary systems for tracking bedsore information, such as the aforementioned Braden Scale, has been developed. However, to date, there have been no systems for continuously tracking bedsore development and status, incorporating this information along with patient mobility on the treatment surface in an automated fashion according to the recorded bedsore status and patient mobility data.
Accordingly, there is an unsolved need for an adjustable pneumatic support surface such as a mattress and the like which is able to diagnose the patient and create a custom designed therapy protocol with the objective of the supporting surface being able to take preventative action before a breakdown of patient tissue occurs. There is a further need for an integrated system capable of tracking and analyzing tissue abnormality development and patient mobility on a pressure relief surface.